Small containers were and are used to package various pharmaceutical substances such as medicines, common aspirin and pills. The recognized danger, of course, was that the caps and lids for such containers were previously not of the safety type and could be removed by small children. Efforts were consequently directed to the development of safety caps which can only be opened in a way impossible for young children or other people to open without knowing the opening technique.
Unfortunately, these efforts produced closure devices which are still not entirely satisfactory. The existing safety closures can be categorized into three groups:
(a) the "palm and twist" types which, although they are impossible for small children to open, present a problem for elderly or handicapped persons because of the applied strength needed; PA1 (b) the "overcap" types which tend to be very expensive and of complex construction because two separate cap parts are used; and PA1 (c) the "deformable" types which generally include a flexible central portion and a deformable peripheral skirt which is released from the upper portion of the container by pressing on the central portion of the cap closure.
Of these three types only type (c) can be considered as potentially the most pertinent because of the above-noted disadvantages inherent in the first two types. For example, the Canadian patent issued to Paul A. Marchant on Aug. 23, 1977, No. 1,016,107 teaches a safety cap characterized by a depressible central circular section 17 and a skirt section 20. When section 17 is depressed downwardly, the skirt 20 is deformed radially outwardly to clear its shoulder 21 from the shoulder 12 of the vial. The drawback of the Patent is that a truly fluid-proof closure is not obtained.
Another Canadian patent issued to Peter A. Vercillo on May 20, 1975 and bearing No. 967,913 discloses another cap, of relatively complicated design, which features a depressible central area and a depending skirt. The cap, however, is dependent in its functionning on the material out of which it is made: this material must be one exhibiting a slot rate of "creep return". In other words, the cap must be removed while the peripheral skirt is in expanded deflected condition and slowly returning to its normal configuration. There is thus an undesirable period of time while the container is not sealingly shut during removal or positioning of the closure cap. Moreover, the safety closure of this patent is of relatively complicated construction as can be seen by referring to the drawings.
Another Canadian Pat. No. 869,854, issued on May 4, 1971 to Lloyd S. Turner discloses a closure cap having a dome-shaped central portion and an integrally-formed downwardly extending peripheral skirt. When dome 17 is subjected to downward pressure the skirt portion 16 expands slightly. Yet, as admitted in the specification of this patent (cf. p. 5, lines 8-14), sometimes a secondary lateral pressure must sometimes be effected against the skirt to ensure the latter properly clears the curved area 13 of the container. There again, no fluid-proof sealing is achieved.
Finally, in the review of the prior art, the U.S. patent issued to Lovell on Jan. 27, 1976 and bearing U.S. Pat. No. 3,934,745 discloses another safety bottle cap belonging to type (c). This patent features another central dome and a downwardly extending skirt portion. An annular ridge 36 is further provided adjacent the upper lip of the container. In theory, depressing the central dome of this patent will cause skirt 24 to expand outwardly, as in previous patents discussed, with ridge 36 acting as a fulcrum for skirt 24. In fact, it has been found that the patent does not function as described: ridge 36 which is intended to form a seal, actually comes to abut against the inner upper surface of container 10 and, contrary to what is intended, really prevents skirt 24 from opening sufficiently outwardly to remove the cap. Fulcrum 36 must be free to slide for proper removal of the cap which it cannot do according to the construction disclosed.
The main feature lacking in all the prior art discussed above is that none of the combinations of a container with a safety closure cap are specifically designed to be fluid-proof, except U.S. Pat. No. 3,934,745. However, the device of this patent cannot function properly.